1. Field of the invention
The present invention relates to a reset mechanism of a counter, for counting the number of times of image formation which is mounted on an image forming apparatus such as an electrostatic process copying machine, a facsimile or a laser beam printer. The reset mechanism resets, at a required time, the counter for counting the number of times of image formation and for reporting the time when maintenance is required.
2. Description of the Related Art
There has been conventionally provided an image forming apparatus so constructed as to bring at least two elements (for example, a photosensitive drum, a cleaning device and a charger) in an image forming section into a unit so that maintenance, such as replacement, can be carried out by integrally removing the unit in cases such as a case where the lifetime of the photosensitive drum is over and a case where the cleaning device is full of waste toner.
There has been also provided an image forming apparatus in which a counter, for counting the number of times of image formation by a photosensitive drum and the like, is provided as means for reporting the time for replacement of such a unit, to display a message or the like issuing an instruction to replace the unit if a value counted by the counter reaches not less than a predetermined value.
In this case, a worker or the like resets the counter to zero after replacing the unit with a new unit, to calculate the next time for replacement of the unit. However, resetting work of the counter is performed manually by the worker. In some cases, the worker may erroneously reset the counter when no reset is required or may forget to reset the counter when reset is required. Therefore, it is impossible to accurately grasp the time for replacement.
In order to solve such a problem, there is provided an image forming apparatus so adapted as to automatically reset a counter in synchronism with the mounting of a unit. In this image forming apparatus, there is no problem if the unit is replaced with a new unit. However, there is a problem when a unit which has not yet been used such a number of times that replacement is required (a unit which has been used, for example, 15,000 times in a case where such a number of times of image formation that replacement is required is 20,000) is removed once and is mounted again. Specifically, even when an old unit which has been used only 15,000 times is mounted again, the counter is reset, so that the unit is used 35,000 times before a message reporting the next time for replacement is issued. Therefore, the time for replacement of the unit greatly slips.